why my Button Style not Show Button content?

See more:

WPF

why my Button Style not Show Button content?
Hello
I Create simply style for button and use ContentPresenter to display My Button Content.But buttoncontent not display.

<Style x:Key="btnStyle" TargetType="{x:Type Button}">
           <Setter Property="Template">
               <Setter.Value>
                   <ControlTemplate TargetType="{x:Type Button}" >
                       <Grid>

                            <ContentPresenter VerticalAlignment="Center" HorizontalAlignment="Center"  ContentSource="Content"/>

                           <Rectangle RadiusX="5" RadiusY="5">


                               <Rectangle.Fill>
                                   <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                                       <GradientStop Color="#FF7C3030" Offset="0" />
                                       <GradientStop Color="#FF271D1D" Offset="1" />
                                       <GradientStop Color="#FF450404" Offset="0.484" />
                                   </LinearGradientBrush>
                               </Rectangle.Fill>

                           </Rectangle>

                       </Grid>

                   </ControlTemplate>
               </Setter.Value>
           </Setter>
           <Setter Property="Foreground" Value="White"/>
       </Style>

 <Button Grid.Row="1" Grid.Column="1"
 Content="ShowWindow" Style="{StaticResource btnStyle}" 
Foreground="White" FontSize="20"/>